Updated copyright notices to include the year 2018.

lib-fts: Fix assert-crash in fts_icu_lcase() Fixes: Panic: file fts-icu.c: line 152 (fts_icu_lcase): assertion failed: (err != U_BUFFER_OVERFLOW_ERROR)

Updated copyright notices to include the year 2017.

global: Use const for all test_functions[] arrays

lib-fts: Change fts_icu_*() to use ARRAY_TYPE(icu_utf16) for UTF16 input. This makes it clearer how the API is intended to be used.

global: Use buffer_get_writable_size() where possible With 09539f3db increasing buffer's init_size with +1 some fts-icu unit tests started failing. And in general it's better to use the writable size since that provides the true size that can be used.

global: freshen copyright git ls-files | xargs perl -p -i -e 's/(\d+)-201[0-5]/$1-2016/g;s/ (201[0-5]) Dovecot/ $1-2016 Dovecot/'

lib-fts: Added fts_icu_lcase()

lib-fts: Call u_clean() at deinit to free up all of libicu's memory.

lib-fts: test-fts-icu memory leak fix

lib-fts: Rewrite ICU handling functions. Some of the changes: - Use buffers instead of allocating everything from data stack. - Optimistically attempt to write the data directly to the buffers without first calculating their size. Grow the buffer if it doesn't fit first. - Use u_strFromUTF8Lenient() instead of u_strFromUTF8(). Our input is already supposed to be valid UTF-8, although we don't check if all code points are valid, while u_strFromUTF8() does check them and return failures. We don't really care about if code points are valid or not and u_strFromUTF8Lenient() passes through everything. Added unit tests to make sure all the functions work as intended and all the UTF-8 input passes through them successfully.